Speed Gene (MSTN) – a gene influencing speed and optimal racing distance

The Speed gene refers to a variant of the MSTN gene, which influences muscle mass development and muscle fiber composition. This gene has a significant effect on the athletic performance of horses, particularly on whether a horse is genetically better suited to short, medium, or long racing distances.

The MSTN gene produces the protein myostatin, which naturally limits the growth of skeletal muscles. In horses carrying the so-called speed mutation (a 227 bp SINE insertion upstream of exon 1), myostatin production is reduced, which promotes the development of muscle mass and fast-twitch muscle fibers. As a result, these horses have a greater genetic predisposition for high speed and explosive performance. However, it is important to emphasize that MSTN is not the only factor determining athletic performance. Optimal racing distance is a multifactorial trait influenced by multiple genes as well as training, nutrition, fitness, and other environmental factors.

The mutation follows an autosomal incomplete dominant inheritance pattern. An individual with the C/C genotype, carrying two copies of the speed variant, has the strongest genetic predisposition for sprints and short-distance races. Heterozygous C/T individuals generally represent a balanced type suited to middle-distance races. T/T individuals, which do not carry the speed variant, are predisposed to longer distances, where endurance is more important than maximum speed.

Knowledge of the MSTN genotype can help to better assess the athletic potential of a young horse, select a suitable discipline and training approach, and plan breeding programs aimed at desired athletic traits in offspring.

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Reference:

Santagostino, M., Khoriauli, L., Gamba, R., Bonuglia, M., Klipstein, O., Piras, F.M., Vella, F., Russo, A., Badiale, C., Mazzagatti, A., Raimondi, E., Nergadze, S.G., Giulotto, E. : Genome-wide evolutionary and functional analysis of the Equine Repetitive Element 1: an insertion in the myostatin promoter affects gene expression. BMC Genet 16:126, 2015. Pubmed reference: 26503543